Method and devices for processing fresh foodstuffs

ABSTRACT

The present invention relates to a method for processing fresh foodstuffs in large quantities and in bulk, such as fruit and vegetables but also other types of foodstuffs such as pasta, fish, meat, etc. in order to allow them to be preserved for a long period of time whilst keeping their organoleptic characteristics. The invention also extends to devices for implementing this method.

SUBJECT OF THE INVENTION

The present invention relates to a method for processing freshfoodstuffs in large quantities and in bulk, such as fruit and vegetablesbut also other types of foodstuffs such as pasta, fish, meat, etc. inorder to allow them to be preserved for a long period of time whilstkeeping their organoleptic characteristics. The invention also extendsto devices for implementing this method.

TECHNOLOGICAL BACKGROUND

The normal techniques of preservation by pasteurization or sterilizationaim to make products preservable for a long period of time whilst tryingto keep their taste and their appearance.

The main difficulty resides in the fact that the products are normallyheated by direct contact, that is to say by conduction or by convectionand most often at high temperatures and for long periods of time, whichmakes the product lose some of its organoleptic and physico-chemicalproperties.

By way of example, let us consider the particular case of techniques forpreserving fruit. For most known techniques relating to the preservationof fruit, the heat treatment of the pieces of fruit produces a puree orstewed fruit which is not suitable for most current industrial orhousehold uses, in particular for cake making.

Various methods for preserving or cooking foodstuffs, which attempt toremedy this problem are known in the state of the art.

In particular, document FR-A-2,635,167 describes an apparatus for steamtreatment of products in a pressurized or vacuum chamber. Although theproducts are apparently treated in bulk, it seems to be necessary toarrange them, for example, on trays or trolleys in order to carry outthe processing in the apparatus.

Furthermore, this processing can in no way be carried out continuouslyor semicontinuously. In fact, the apparatus has to be stopped in orderto introduce the foodstuffs into the pressurized or vacuum chamber.

Document EP-A-0,006,369 describes a method for continuous heat treatmentof unpackaged or packaged bulk products in a casing in which a vacuum isset up; this vacuum is then broken by an external supply of steam. Thisstep has the consequence of pressurizing the casing.

Document CA-A-975,976 describes a method for cooking foodstuffsaccording to which water is heated to boiling in an enclosed container,and air and some of the steam created in this container are expelled soas to obtain a partial vacuum therein, the cooking is carried out underpartial vacuum and this partial vacuum is terminated before removing thefoodstuffs from the container. This method which is described obviouslydoes not allow continuous or semicontinuous treatment. Again, themachine should be completely stopped before extracting the foodstuffs.

Document U.S. Pat. No. 4,543,283 describes an apparatus and a methodwhich are intended for heating and cooling foodstuffs continuously, inwhich the steam treatment container is under pressure.

OBJECTS OF THE INVENTION

The invention aims to provide a method for preservation of freshfoodstuffs which avoids the drawbacks of solutions of the state of theart and more particularly aims to develop a processing method whichprovides better guarantees of preserving the organoleptic andphysico-chemical characteristics of the treated product.

In particular, it is desired to obtain a method which operatescontinuously or semicontinuously and which allows the foodstuffs treatedto be packaged directly on leaving the treatment device.

The method according to the invention is more precisely intended forwhat is termed "aseptic filler" or "hot filler" techniques, which may beexpressed in French as techniques of aseptic filling orself-pasteurization, without cooling.

The invention also relates to devices (installations) for implementingthe said method.

MAIN CHARACTERISTIC ELEMENTS OF THE INVENTION

The present invention relates to a method for preservation of bulk freshfoodstuffs by heat treatment, characterized in that the foodstuffs areintroduced into a reduced-pressure chamber and in that these foodstuffsare subjected to a flow of steam in a direction opposite to that oftheir movement, this steam condensing on the foodstuffs and beinggenerated from water released from the foodstuffs and optionally fromthe added covering liquid which is necessary for aseptic filling.

According to the present invention, the heat can in this way betransmitted to the product in its bulk, that is to say without needingto agitate or manipulate the product and therefore without it becomingdamaged.

The processing of foodstuffs according to the present invention can becarried out with a semicontinuous continuous method, and also with acontinuous method, advantageously in a very short space of time of theorder of 5 to 6 minutes.

Furthermore, the method according to the present invention is carriedout without an external supply of steam being necessary.

The device for implementing the method according to the inventionessentially comprises a vessel under reduced pressure with respect toatmospheric pressure, into which the foodstuffs are introduced and areheated by condensation of steam which comes from the bottom of thevessel and in which the foodstuffs move under gravity towards the bottomof the vessel whilst the steam moves in counter-flow with respect to thefoodstuffs.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents a diagrammatic view of the device according to theinvention, allowing implementation of the method.

FIG. 2 represents a detailed view of the reduced pressure vesselaccording to FIG. 1.

FIG. 3 represents a diagrammatic view of another preferred device of theinvention, corresponding to an alternative embodiment of the method.

FIG. 4 represents a diagrammatic view of another preferred device of theinvention, corresponding to another alternative embodiment of themethod.

The same reference numbers are used in the various figures to representidentical or similar elements.

DETAILED DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS OF THE INVENTION

As is shown by FIGS. 1 and 2, the foodstuffs, for example fruit, areintroduced into a vessel which is under reduced pressure with respect toatmospheric pressure and given the general reference 2, via an airlock 1which operates by compartmentalization.

In preference, this airlock 1 which is intended to introduce thefoodstuffs into the vessel 2 is equipped with a variable-speed gear anda frequency converter which is coupled to a positive displacement pump 5arranged at the exit of the vessel 2 and which removes the producttherefrom.

The reduced-pressure vessel 2 is essentially composed of an upperchamber 3 and one or more lower housings 4 separated from the enclosure3 by perforated grids 7.

The chamber 3 is connected via a condenser 11 to a vacuum pump 9.

This condenser 11 may operate in various modes. For example, thecondensation may be obtained by preferably spraying droplets of waterinto the condenser, or a cold water pipeline is alternatively directlyfitted to the condenser and connected to a vacuum pump, preferably astainless steel ring water pump.

The operation of the airlock i necessarily brings air in through theairlock itself and consequently causes loss of pressure reduction. Thepump must therefore be capable of continuously compensating for thispressure reduction loss so as to obtain a constant pressure P₁ (lessthan atmospheric pressure P_(a)) in the chamber 3 when the apparatus isoperating.

The covering liquid coming from a tank 15 is introduced into thereduced-pressure vessel 2 via a flowmeter 17 which regulates thecovering liquid supply using a differential-pressure valve 19.

More precisely, this covering liquid which is intended for filling thepreserving containers (can or bag) during the covering liquid additionstage, is introduced into the housing or housings 4 arranged between thebottom of the vessel 2 and the perforated plates 7. This covering liquidis heated via a double wall 13 which is itself heated by circulation ofsteam coming from an external circuit 14.

Other heating means are obviously not precluded.

Consequently, in the housing or housings 4 bounded by the perforatedplates 7, a pressure P₂ prevails which is greater than P₁ prevailing inthe upper chamber 3, that is to say that the reduced pressure prevailingin the housing 4 is less strong than that in the chamber 3.

Because of this, there is a movement of steam which is constantly formedfrom the covering liquid coming from the housing 4 towards the upperchamber 3 through the perforated plates 7. This steam condenses uponcontact with the foodstuff which is at a lower temperature, thusproviding it with the heat supply necessary for pasteurizing thefoodstuff.

Furthermore, foodstuffs which lie in the uppermost layers of the upperchamber 3 have the oxygen present in their tissues removed because ofthe reduced pressure P₁ prevailing in this chamber.

As the foodstuff descends in the reduced-pressure vessel 2, it is heatedconstantly, layer by layer, by condensation of steam.

At a determined level, the foodstuffs comes into contact with thecovering liquid and is sucked up by the positive displacement pump 5 andthen leaves the reduced-pressure vessel 2. This prevents a "floating"during the suction on the foodstuff with the covering liquid and perfectmixing of the pieces of foodstuff such as fruit with the covering liquidthereby is obtained.

The product is then pumped towards a scraped-surface exchanger 35 beforereaching a "holding" treatment unit 37 where the sterilization iscarried out and a cooling unit, not represented, before aseptic fillingof, for example, bags.

Any other kind of heat exchanger can be used instead of ascraped-surface exchanger.

The device also comprises several sensors or detectors which areintended to monitor its operation.

In the upper part of the reduced-pressure vessel 2, an electronicpressure detector 23 has been arranged, together with a safety valve 21which allows removal of the excess steam when an excessively highoverpressure peak has been reached.

In preference, this detector 23 will directly control the supply ofsteam in the external circuit 14 which heats the double wall 13, thisbeing as a function of data additionally supplied by a temperaturedetector 25.

It is also possible to provide a safety detector 20 which monitors thepresence of covering liquid on the double wall 13.

According to a second preferred embodiment of the present invention,foodstuffs having a pH greater than 4 such as meat, vegetables, fish,etc., can be treated in a device described in FIGS. 3 and 4.

In this case, the sterilization temperature is greater than 100° C.,and, as represented in FIG. 3, the foodstuffs are sucked up upon leavingthe reduced-pressure vessel 2 by a positive displacement pump 5 beforebeing introduced into a second chamber 27 which is under pressure. Thepressure in this chamber is higher in the lower part than in the upperpart. This chamber is also heated by means of a double wall 24 which isitself heated using steam coming from the external circuit 14.Temperatures greater than 110° C. are easily achieved in this way.

The foodstuffs are then sucked up by a steam barrier pump 33 locatedbelow the pressurized chamber 27 and are conveyed to the treatment unit37 and the cooling stage 39 before aseptic filling is carried out.

This arrangement is preferably used for foodstuffs which have asterilization temperature lying between 100° and 115° C.

For foodstuffs requiring a higher temperature (greater than 115° C.),the pump 33 will preferably be placed between various cooling stages 39and consequently at a location where the temperature has alreadydecreased, for example reached about 100° C. (see FIG. 4).

The main advantage of this arrangement is that the product is no longeras decomposable and therefore vulnerable during the pumping by the pump33. In this case, it should be noted that it is not necessary for thepump 33 to operate synchronously with the positve displacement pump 5.

I claim:
 1. Method for preservation of bulk fresh foodstuffs by heattreatment, comprising:introducing the foodstuffs into a reduced-pressurechamber through an air lock thereby maintaining the reduced pressure inthe chamber, moving the foodstuffs in a pre-defined direction of travelin the chamber, subjecting the foodstuffs in the chamber to a flow ofsteam wherein the steam flow is in a direction opposite the direction oftravel of the foodstuffs, and providing some of the heat necessary forheating the foodstuffs by allowing steam to condense on the foodstuffsin the chamber.
 2. Method according to claim 1, which includesgenerating the steam in the chamber without an external supply of steam,the steam being generated from the water released from the foodstuffsand from a covering liquid necessary for aseptic filling.
 3. Methodaccording to claim 1, characterized in that the steps of the methodoccur in a continuous cycle.
 4. The method claim 1 wherein said movingthe foodstuffs in a pre-defined direction of travel includes moving thefoodstuff in a vertical direction of travel under the influence ofgravity.
 5. A device for preserving bulk fresh foodstuffs by heattreatment, comprising: a vessel (2) under reduced pressure with respectto atmospheric pressure, means for introducing the foodstuffs into saidvessel, which vessel includes means for moving the foodstuffs in apre-determined direction in said vessel and wherein the foodstuffs areheated by the condensation of a flow of steam moving in a directionopposite to the direction of movement of the foodstuffs, which furtherincludes an airlock (1) which provides an entry for the foodstuffs intosaid vessel, and a positive displacement pump (5) located at the exit ofsaid vessel (2), which removes the foodstuffs therefrom.
 6. The deviceclaim 5, wherein the reduced-pressure vessel includes an upper chamber(3) in which a constant pressure less than atmospheric pressure prevailsand at least one lower housings (4) separated from said upper chamber(3) by perforated grids (7), in which a pressure (P₂) prevails which isgreater than the pressure (P₁) prevailing in the upper chamber (3). 7.The device of claim 6, wherein said upper chamber (3) is connected to avacuum pump (9) via a condenser (11).
 8. The device of claim 6 whichfurther includes a tank (15) for introducing covering liquid into saidhousing (4) which is located between the bottom of the vessel (2) andthe perforated grids (7).
 9. The device of claim 8, wherein the coveringliquid is heated via a double wall (13) which is itself heated by a flowof steam coming from an external circuit (14).
 10. The device of claims5 which further includes sensors (20, 21, 23 and 29) which monitor theoperation of the device.
 11. The device of claim 5 which furtherincludes a pressurized chamber (27) having a top portion and a bottomportion, wherein the pressure in the pressurized chamber (27) is higherin the top portion than in the bottom portion, and wherein saidpressurized chamber (27) is connected to said reduced-pressure vessel(2) through said positive displacement pump (5), and wherein thefoodstuffs are transported to said pressurized chamber (27).
 12. Thedevice of claim 11, which includes a second pump (33) which sucks thefoodstuffs out of said pressurized chamber (27).
 13. The device of claim12 which further includes a cooling unit (35) having multiple stagestherein, and wherein said second pump (33) is located between two ofsaid multiple cooling stages of said cooling unit (35).
 14. The deviceof claim 12, which further includes a cooling unit (35) and wherein saidsecond pump (33) is located between said pressurized chamber (27) andsaid cooling unit (35).